llvm.experimental.stackmap: fix encoding of large constants.

In the stackmap format we advertise the constant field as signed.
However, we were determining whether to promote to a 64-bit constant
pool based on an unsigned comparison.

This fix allows -1 to be encoded as a small constant.

llvm-svn: 198816

1 files changed, 4 insertions, 1 deletions

diff --git a/llvm/lib/CodeGen/StackMaps.cpp b/llvm/lib/CodeGen/StackMaps.cpp
index 1dc76d5c6a6..d70e6b30448 100644
--- a/llvm/lib/CodeGen/StackMaps.cpp
+++ b/llvm/lib/CodeGen/StackMaps.cpp
@@ -207,7 +207,10 @@ void StackMaps::recordStackMapOpers(const MachineInstr &MI, uint64_t ID,
   // Move large constants into the constant pool.
   for (LocationVec::iterator I = Locations.begin(), E = Locations.end();
        I != E; ++I) {
-    if (I->LocType == Location::Constant && (I->Offset & ~0xFFFFFFFFULL)) {
+    // Constants are encoded as sign-extended integers.
+    // -1 is directly encoded as .long 0xFFFFFFFF with no constant pool.
+    if (I->LocType == Location::Constant &&
+        ((I->Offset + (int64_t(1)<<31)) >> 32) != 0) {
       I->LocType = Location::ConstantIndex;
       I->Offset = ConstPool.getConstantIndex(I->Offset);
     }